The use of multipath analog-to-digital converters (ADCs) and analog front ends (AFEs) (e.g., two or more path ADCs/AFEs) in electrical circuits is known. Example multipath ADCs and AFEs and use of them in multiple electrical circuit paths are disclosed in U.S. patent application Ser. No. 14/476,507 entitled “Multi-Path Analog Front End and Analog-to-Digital Converter for a Signal Processing System” to Schneider et al. filed Sep. 3, 2014, U.S. patent application Ser. No. 14/480,180 entitled “Multi-Path Analog Front End and Analog-to-Digital Converter for a Signal Processing System” to Schneider et al. filed Sep. 8, 2014, U.S. patent application Ser. No. 14/480,263 entitled “Multi-Path Analog Front End and Analog-to-Digital Converter for a Signal Processing System” to Schneider et al. filed Sep. 8, 2014, and U.S. patent application Ser. No. 14/480,343 entitled “Multi-Path Analog Front End and Analog-to-Digital Converter for a Signal Processing System” to Schneider et al. filed Sep. 8, 2014 (collectively, the “Schneider Applications”). The use of multipath circuits may reduce noise as one path may be optimized for processing small amplitude signals (e.g., for processing low noise signals) while another circuit path with another set of ADC and AFE may be optimized for large amplitude signals (e.g., allowing for higher dynamic range).
An example application for multipath ADCs/AFEs is use in a circuit for an audio system application, such as an audio mixing board or in a digital microphone system. In designing a circuit with multipath ADCs/AFEs that are used in respective multiple circuit paths, a tradeoff may exist between allowing larger signal swing (e.g., to allow swing of a signal between larger scale amplitudes) and low noise. Furthermore, the multipath ADCs/AFEs may provide high dynamic range signal digitization, with higher dynamic range for a given input power, and lower overall area than would be possible with conventional means. In other words, by allowing a separate optimization for each type of signal (e.g., large and small signals) that is provided each respective path, multipath ADCs/AFEs allow the overall circuit to burn less power, consume less area, and save on other such design costs.
Despite their advantages, existing multipath ADC/AFE approaches have disadvantages and problems. For example, many existing approaches have disadvantages related to transitioning and switching between the multiple paths, as such switching may not be smooth, leading to undesirable signal artifacts, especially in audio applications in which such artifacts may be perceptible to a listener of an audio device. For example, when switching between two paths in a multipath AFEs/ADCs, the paths may have different noise floors, which may create an artifact sometimes referred to as a “breathing” artifact. In addition, in existing implementations, switching thresholds for switching between paths may not provide for the highest performance of an audio system at all frequency levels.